Have a 1993 Gulfstream Sunsport with a Chevy 454. It won't start even when jumped. Would not start even when jumper cables were hooked up to a running Ford V8 vehicle for 20 minutes. Disconnected jumper cables. Plugged motorhome into landline. On a whim I decided to try starting it and it started right up. Why wouldn't it start when jumped from another vehicle, but it would start when plugged into a landline?